1. Field of the Invention
The present invention relates generally to workpiece authentication techniques, and more specifically, to such techniques which involve imaging one or more portions of the workpiece to generate abstractions (e.g., numeric or alphanumeric strings) which represent random physical characteristics of the workpiece that may be used to determine whether the workpiece is authentic. Although the present invention will be described in connection with authenticating postal mailpieces based upon such abstractions, it should be appreciated that the present invention has other utilities, including authenticating workpieces other than postal mailpieces.
2. Brief Description of Related Prior Art
A value indicium is a symbol or token that indicates payment for a service. One example of a commonly-used value indicium is the “franking” or postal meter mark, which is placed on a postal mailpiece to indicate that a specified amount of money has been paid to post the mailpiece. Other examples of value indicia include paper currency, money orders, and tickets for cultural events and transportation.
Authentication indicia are symbols or tokens placed on or in a workpiece for use in determining the validity of the workpiece (e.g., whether the workpiece is authentic, as opposed to being a forgery). For example, legal documents, such as passports and driver's licenses often have validation stamps/seals from a certifying authority (CA), such as the government, placed on them that vouch for the authenticity of the legal documents.
In the past, if a postal franking mark on a postal mailpiece appeared to the ordinary observer (e.g., a postal clerk) to have been made by an authorized postal franking device, the mailpiece would be considered valid and would be posted without further inquiry into whether the mark was genuine. Unfortunately, improvements in photocopying, computer-based imaging and duplication technologies have rendered this prior art authentication technique unreliable, as they have permitted the unscrupulous to produce high quality forgeries of such franking marks that often appear genuine to the ordinary observer. This has driven interest in creating a postal franking mark whose authenticity can be determined without reference to its appearance, but instead can be determined using different criteria.
In one such conventional validation technique, the franking mark comprises an indicium that contains certain identifying information, such as the postage purchase date, meter identification number, franking sequence number, source and destination addresses of the mailpiece, and a cryptographic signature of the identifying information. According to this technique, mailpiece forgeries are detected based upon whether differences exist between the identifying information and the cryptographic signature in the indicium, and the actual identifying information of the mailpiece and the actual cryptographic signature of such actual identifying information.
Unfortunately, this latter validation technique is unable to thwart certain types of postal franking fraud. For example, if the identifying information and signature of a valid indicium of a first mailpiece are also valid for a second mailpiece, then the indicium of the first mailpiece may be fraudulently copied onto the second mail piece, and the fraudulent copying cannot be detected using this technique. Hereinafter, this type of fraud will be termed “double spending fraud.”
Additionally, advances in networking technology have also permitted wide access to the data underlying such franking marks. For example, one could download such data using the Internet from a computer node storing such data (e.g., via email or a World Wide Web posting), and depending upon the manner in which this conventional technique is implemented, a large number of seemingly valid franking marks could be generated based upon such data. This further exacerbates the possibility and opportunity for such fraud.
In one prior art technique that is used to try to thwart double spending fraud, a database tracks use of value indicia and the respective identifying information therein. If two mailpieces have identical indicia, the database indicates this as a possible occurrence of double spending fraud.
Unfortunately, in practical implementation, this conventional double spending fraud detection technique requires use of a large database to track the indicia's identifying information. Disadvantageously, the burden and expense of maintaining and querying such a large database is undesirable. Also disadvantageously, this conventional fraud detection technique does not permit off-line verification of the indicia (i.e., not based upon information obtained via a network), and no mechanism is provided in this technique to determine which indicium among indicia determined to be identical is authentic.
Another prior art fraud problem arises when unauthorized use is made of data or digital tokens (e.g., stored in a computerized postal franking system's internal memory) that when supplied to the system cause it to produce otherwise valid authentication indicia. This type of fraud will be termed hereinafter “meter tampering double spending fraud.”
Other examples of prior art are disclosed in e.g., Melen, U.S. Pat. No. 5,325,167 issued Jun. 28, 1994; Daugman, U.S. Pat. No. 5,291,560 issued Mar. 1, 1994; Causse D'Agraives et al., U.S. Pat. No. 4,677,435 issued Jun. 30, 1997; Samyn, U.S. Pat. No. 4,820,912 issued Apr. 11, 1989; Goldman, U.S. Pat. No. 4,423,415 issued Dec. 27, 1983; Goldman, U.S. Pat. No. 4,568,936 issued Feb. 4, 1986; Brosow, U.S. Pat. No. 4,218,674 issued Aug. 19, 1980; Deneberg et al., U.S. Pat. No. 5,521,984 issued May 28, 1996; Sansone, U.S. Pat. No. 4,725,718, issued Feb. 16, 1988; and Fougery et al., U.S. Pat. No. 4,743,747, issued May 10, 1988. Each of these patents is incorporated herein by reference in its entirety.